The road to Baghdad: A timeline of events in the Iraq war
Military action began in March 2003 but how did it start and did it ever end?
On March 18, 2003, the House of Commons voted to approve British military action in Iraq to disarm Saddam Hussein.
This was the fifth military intervention of Tony Blair's premiership and his second foray into Iraq following a four-day bombing campaign the UK and US conducted on Iraqi targets in 1998.
For Blair, it would prove to be the costliest of all his wars for his future and legacy as Prime Minister.
The March 18 vote was both the culmination and the beginning of a series of political, diplomatic and military developments that would change the face of the UK, the Middle East and the world.
A new century
At the turn of the 21st century, Saddam Hussein's Iraq had been living under comprehensive UN-imposed sanctions for over nine years.
The strict limits sanctions imposed on both imports and exports were linked to rises in infant mortality, malnutrition, a lack in medical supplies and the proliferation of diseases resulting from a lack of clean water.
The effects of these sanctions were a "true human tragedy", said senior UN official in Iraq Hans von Sponeck in February 2000.
Yet the sanctions were deemed a success by many in that they compelled Hussein to co-operate with the UN with regards to weapons inspections and monitoring.
The import restrictions also prevented both any conventional military build-up and the import of materials that could have advanced a programme for weapons of mass destruction.
Then the September 11 attacks in New York, as the saying goes, "changed everything".
The war on terror was launched in Afghanistan in 2001, with Iraq named by US president George Bush as a member of the "axis of evil" in his state of the union address in January 2002.
In September of that year, the UK published a dossier that claimed Iraq could build a nuclear weapon within one to two years, and also suggested Hussein had the capability to launch existing chemical and biological weapons within 45 minutes of the order being given.
The UN passed a resolution in November that promised "serious consequences" for the Iraqi dictator if he did not comply with weapons inspectors.
In January 2003, the UK accused Iraq of being in "material breach" of UN disarmament requirements and began, along with the US and Spain, to push for a second UN resolution backing military action if Hussein did not meet an ultimatum to disarm by March 17.
Despite failing to get security council support for this resolution, Bush gave Hussein 48 hours to leave Iraq or face invasion in a televised address at 1am on March 18.
Later that day, the UK Parliament voted to back military action by 412 votes to 149 despite Blair suffering a backbench rebellion.
An amendment opposing military intervention was backed by 271 MPs - including 139 from the Labour benches - but it was defeated by 396 votes.
The UK was at war.
The US launched its first air strikes on Baghdad in the early hours of March 20, while later that day British marines launched an amphibious assault the al-Faw peninsula in southern Iraq.
The following day coalition forces began an aerial bombardment on Baghdad that the Pentagon dubbed a "shock and awe" strategy.
On April 6, British forces entered Iraq's second city, Basra, and three days later civilians in Baghdad toppled a statue of Saddam Hussein in Firdos Square with the help of US troops.
On May 1, Bush declared the end of major combat operations on an aircraft carrier bearing a banner reading Mission Accomplished.
Yet on the same day, seven US troops were injured in a grenade attack on Fallujah, in a sign of things to come.
In July, Hussein's sons Uday and Qusay were killed in a firefight in Mosul, while in August the notorious Chemical Ali was captured.
But the guerrilla resistance to occupation forces continued to grow and launch more attacks.
On December 13, a bearded Saddam Hussein was captured in an underground hide-out near his hometown of Tikrit.
By May 2004, the number of British troops had fallen from a peak at the start of the war of 46,000 to 8600 as coalition forces attempted to transfer territorial control across the country to fledgling Iraqi forces.
In January 2005, Iraq voted in its first democratic elections since the 1950s but the Sunni/Shia sectarian violence that would blight the following years had already taken root.
The bombing of a Shia shrine in Samarra in February 2006 sparked a wave of sectarian bloodshed that would eventually cause the US to launch a troop "surge" in Baghdad and the Anbar province to try and pull the country back from the brink of civil war.
The death of Corporal Gordon Pritchard of the Royal Scots Dragoon Guards in January 2006 took the number of British troop casualties in Iraq to 100.
Two months later, defence secretary John Reid announced the first phase of Britain's withdrawal from the country, with 800 troops sent home, and a further 1600 announced by Blair at the start of 2007.
On December 30, 2006, Saddam Hussein was executed by hanging.
By 2007 the US "surge" had begun in earnest, with five combat brigades and around 30,000 soldiers sent to Iraq between February and June.
This troop increase accompanied overtures by the US-backed Iraqi government to Sunni tribes in the region, encouraging them to turn against Al Qaeda in Iraq, who were orchestrating much of the sectarian violence on the Sunni side.
After Blair resigned in June 2007, new Prime Minister Gordon Brown accelerated plans to withdraw British servicemen and women from the country, with Basra - the last of the four provinces that had been under UK control - handed over to Iraqi forces by the end of the year.
In December 2008, Brown announced UK forces would be withdrawn from Iraq by July 2009.
In fact, nearly all of the remaining 3700 British troops began leaving Iraq after the end of British combat operations was formally announced on April 30, 2009.
The US, too, began its own phased withdrawal from the country, with newly inaugurated president Barack Obama announcing plans to end combat operations by 2010 while leaving a residual 50,000-strong US force to train the Iraqi army.
All US combat troops had left Iraq by the end of 2011.
Not the end
It was less than three years later, in the summer of 2014, that Islamic State - which grew from Al Qaeda in Iraq - launched a stunning offensive to capture the city of Mosul in Iraq.
From there, it went on to claim swathes of territory in both Syria and Iraq, taking advantage of the chaos and sectarian unrest in both countries.
British and American military personnel are back in Iraq today, fighting this new enemy.
The war launched in 2003 changed the Middle East and the world, and also irrevocably altered the fortunes of a British Prime Minister.
The anticipation felt across the political spectrum for the publication of the Chilcot Report is testament to the war's enduring legacy on British politics.